1. Field of the Invention
The present invention relates generally to a portable Internet (WiBro: Wireless Broadband) system, and in particular, to a system and method for determining a position based on the portable Internet, for enhancing an accuracy of a position of a mobile communication terminal in a portable Internet system.
2. Description of the Related Art
In recent years, the position determination technology has been expanded for application to various fields, such as vehicle and ship navigation and a mobile communication terminal. Popular position determination methods include, for example, determining a position using a Global Positioning System (GPS) signal, and using a signal from a Base Station (BS).
The position determination method using the GPS signal refers to a method for calculating, by a mobile communication terminal equipped with a GPS receiver, a distance between a GPS satellite and the GPS receiver using a code carried on the GPS signal transmitted by the GPS satellite, and determining the position using the distance.
The position determination method based on the signal from the BS is a Time Difference Of Arrival (TDOA) method for calculating a distance between the BS and a mobile communication terminal using pilot signals received from at least three BSs, and determining the position using the calculated distance.
The GPS-based position determination method can easily determine the position because a strength of the GPS signal is high when the sky is clear (or free of obstacles). However, in the circumstances such as downtowns where there are many buildings, a shadow area and the indoors, it is impossible for the method to determine the position because the strength of the GPS signal is weak.
Undesirably, a method for determining a position using a pilot signal cannot detect both a weak pilot signal transmitted by a neighbor BS and a pilot signal on a direct path weakened due to an obstacle, when a mobile communication terminal is located very close to an arbitrary BS. Accordingly, the position determination methods require the development of a technology for enhancing the accuracy of determining the position of the mobile communication terminal.
As described above, the GPS-based position determination method is used because it is easy to acquire the GPS signal when the sky is clear. The position determination method using the pilot signal is used because it is easy to acquire the pilot signals from the neighbor BSs when there exist the sufficient number of neighbor BSs receiving a signal of the mobile communication terminal. However, even in the position determination method using the pilot signal, there may occur the circumstances where the signal of the neighbor BS cannot be detected because the signal transmitted by the BS strengthens in mid course. Under these circumstances, there is a need to provide an improved system and method for exactly estimating the position of the mobile communication terminal.